Material such as powder or particulate material is often housed in bulk in a silo or bin, from which it is to be discharged periodically. The silo generally has a tapering, usually conical, outlet. The material is, in proposed apparatus, urged through the outlet by a bin activator which is in the form of a cone mounted in the outlet and which is vibratable in a horizontal direction, that is in a direction generally at right angles to the longitudinal axis of this opening. The cone is vibratable by a vibrator situated externally of the silo. The cone is smaller in diameter than the inside diameter of the outlet so that an outlet annulus is defined between the cone and the outlet and through which the material flows. The purpose is not only to discharge the powder, but to consolidate, deaerate and condition the powder prior to discharge. Because of the deaeration and consolidation, the powder will bridge over the annular outlet, and thus obturate it, when vibration of the cone ceases. The annular outlet thus has to be carefully sized for each material being handled; in other words the prior apparatus can only handle a particular material. The apparatus is thus material condition dependant.